LU-10185 gnilnd: SLES 12 SP2 support and cleanup

LU-10185 gnilnd: SLES 12 SP2 support and cleanup

Handle a couple changes for SLES 12 SP2:
 - Handle rename of set_mb() to smp_store_mb()
 - Handle rename of __GFP_WAIT to __GFP_RECLAIM
 - Handle parameter change to sock_create_kern()

Also remove various dead code.

Test-parameters: trivial

Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I9b5799a492b347fe7961f2d70e24bed5cc2e7021
Reviewed-on: https://review.whamcloud.com/29892
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Doug Oucharek <dougso@me.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>